The rate of Mexican migration to the United States has declined precipitously in recent years. From 15.6 migrants per thousand residents in 2005, the annual international migration rate for Mexican adults dropped to almost 4 per thousand by 2011. If sustained, this low migration rate is likely to have a profound effect on the ethnic and national-origin composition of the U.S. population. Given the disparities in health and social wellbeing between the immigrant and native populations, the lower migration rate may also have important implications for public policy in the years to come. Yet so far we do not fully understand the origins of the decline in Mexico-U.S. migration, or the associated changes in the characteristics of individuals that are more likely to migrate. Previous studies rely largely on a descriptive analysis of migration trends and are therefore unable to systematically test competing explanations against each other. In this study I will use data from the Mexican National Occupation and Employment Survey (Encuesta Nacional de Ocupaci?n y Empleo, ENOE), a nationally-representative panel survey of Mexican households conducted on a quarterly basis, to estimate the decline in Mexico-U.S. migration from 2005 to 2012. I will also test the effect that the slowdown in economic growth and reduction in labor demand in different sectors of the U.S. economy had on the rate of international migration from Mexico. Finally, I will examine changes in the selectivity of Mexican migrants during the period of rapidly declining migration. In particular, I will consider whether changing economic conditions in the U.S. led to shifts in the educational selectivity of international migrants. Understanding the causal origins f the decline in migration from Mexico may give us an indication of the direction of future trends. I the decline is primarily a result of worse employment prospects for migrants as a consequence of the U.S. recession, then Mexican migration may be expected to pick up again as the economy recovers. If, on the contrary, the decline is due to more permanent changes in the Mexican economy or demographic changes that are not easily reversible (such as fertility changes), then the migration rate may be expected to remain low. Estimating the changes in the gender, age and educational selectivity of migrants is important because such changes will affect the relative composition of the foreign-born population in the U.S., with possible long-term implications for labor markets and health disparities.